West Nile virus infection is an emerging infectious disease in the United States. The virus infects birds, which serve as the natural reservoir for the virus, in addition to humans and horses which are incidental hosts. It is an arthropod-borne virus, being transmitted by the Culex mosquito. Since 1999, the virus has rapidly spread throughout the continental U.S. Human cases of West Nile disease have been documented in 45 states of the continental U.S. including the west coast. In 2003, a total of 9,377 cases were reported with 244 deaths. About 30% of these cases showed indications of neuroinvasion. These clinical findings are significantly worse in elderly patients, in whom the case fatality rate approaches 30%. Currently, there is no approved commercially available vaccine for prevention of West Nile virus infection in humans. There is also no specific therapy for disease, only symptomatic treatment. In addition to natural infection, West Nile virus has the potential to be used as an agent of bioterrorism. The virus is currently listed as a category B priority pathogen by the NIAID. [unreadable] The ultimate goal of this research and development project is to produce a safe and effective vaccine for West Nile virus infection in humans. The candidate vaccine is a recombinant subunit vaccine in which the immunogens are a modified envelope protein plus a non-structural protein from the West Nile virus. The recombinant proteins are produced by a proprietary method of expression and purified by immunoaffinity chromatography. In phase I research, Hawaii Biotech demonstrated the immunogenicity and protective efficacy of this vaccine in an animal model of disease. The objectives of the present phase II research proposal are the pre-clinical development of the vaccine, including vaccine formulation and additional efficacy studies in animal models including non-human primates, as well as the production of well characterized antigens, and their use in GLP toxicology studies. [unreadable] [unreadable]